To implement T374863: Prevent global autoblocks on a configurable list of IP addresses, we should add a on-wiki message on the GlobalBlockingCentralWiki (defined as metawiki on WMF wikis) that lists IP addresses that are exempt from global autoblocks. This task is to create the message for this list and also create a service that allows interacting with the list, which will work similar to MediaWiki core's AutoblockExemptionList service.
Acceptance criteria
- Add a service to GlobalBlocking that allows callers to know if a IP address is exempt from global autoblocks, by reading the on-wiki message (this being similar to MediaWiki core's AutoblockExemptionList service).